Overflow outlet for a cyclone separator and method of operation

ABSTRACT

A cyclone separator (10) having an elongated tapered separating chamber (25) with tangential inlet pipes (26, 28) thereto, and overflow outlet pipe (34) at the larger diameter end of the separating chamber, for outflow of a less dense component of a liquid mixture to be separated, and an underflow outlet (23) at the smaller diameter end of the separating chamber, for outflow of the denser component of the liquid mixture to be separated. The overflow outlet pipe (34) has an orifice (77) which is variably obstructable by a valve member (80) movable lengthwise of the pipe (34), to vary the flow rate through the outlet pipe (34). The degree of contamination of the denser liquid component emerging from the underflow outlet (23) is monitored by a detector (118) which is connected to a control circuit (108) which controls a motor (110). Motor (110) is coupled to valve member 80 whereby to move the valve member towards and away from the orifice (77), whereby to decrease the flow through outlet pipe (34) when the contamination level drops and to increase flow when the contamination level rises. A further control circuit (140) coupled to detector (118) is effective to control valves (102, 104) whereby to recycle the denser liquid component through the separator in the event that the contamination level is determined to be above a predetermined level.

This invention relates to a cyclone separator for separating liquidcomponents in a liquid mixture and having an elongate tapered separatingchamber with at least one side inlet for liquid to be separated and anoverflow outlet opening at a larger cross sectional end of theseparating chamber, for outflow of the less denser of said components,the separating chamber also having an underflow outlet at the smallercross sectioned end of the separating chamber, for outflow of the denserof said components. The invention is particularly, but not exclusivelyconcerned with separators of this kind and which are specificallyadapted for separating oil and water.

U.S. Pat. No. 4,237,006 (Colman et al) describes a cyclone separator ofthe above kind, the separating chamber having first, second and thirdcontiguous cylindrical portions arranged in that order, the firstcylindrical portion being of greater diameter than the secondcylindrical portion and the third cylindrical portion being of lesserdiameter than the second cylindrical portion, the overflow outlet of theseparator communicating with the first cylindrical portion at the endthereof opposite to said second cylindrical portion and there being aplurality of and a plurality of tangentially directed feed inletscommunicating with the first cylindrical portion. My InternationalApplication PCT/AU83/00028 entitled "Cyclone Separator" and filed Feb.28, 1983 also describes a similar type of separator.

It has been found that the selection of the cross sectional area of theoverflow outlet is critical for proper performance of the separator, butthat a cross sectional area which is suitable for some operatingconditions may not be suitable for other operating conditions. Thus,when the separator is used in an environment where the operatingconditions vary, inadequate separation may be achieved, with substantialcontamination of, say, the emergent denser liquid component due topresence of excessive amounts of the less dense component. Thesevariations may, for example, occur due to variations in the proportionsof the two components in the mixture supplied to the separator forseparating, or by variations in flow rate through the separator.

In accordance with one aspect of the invention, there is provided acyclone separator as first above described wherein valve means isprovided operable to effect variable restriction of flow from theseparator via said overflow outlet opening. Preferably, the overflowoutlet presents an orifice through which liquid flow from the overflowoutlet occurs in use of the separator and the valve means comprises amember such as a needle member movable to variably obstruct the orifice.

Where the overflow outlet presents a stepped bore having a first boreportion adjacent the first cylindrical portion, the stepped bore may beconfigured as described in my international application PCT AU83/00028.

The invention is further described by way of example only with referenceto the accompanying drawings in which:

FIG. 1 is a perspective view, partly sectioned, of an exemplary cycloneseparator which the invention is applicable; and

FIG. 2 is an enlarged fragmentary cross-sectional view of the overflowoutlet of the separator of FIG. 1;

FIG. 3 is a diagram showing control means useful with the separator ofFIGS. 1 and 2;

FIGS. 4 and 5 are diagrammatic cross sections of valves incorporatedinto the control means of FIG. 3, and showing conditions of the valvesprevailing in one operative condition of the control means;

FIGS. 6 and 7 are diagrammatic cross sections like FIGS. 4 and 5respectively, but showing the valves in conditions prevailing in anotheroperative condition of operation of the control means; and

FIG. 8 is a diagram showing a modified control means useful in theseparator of FIGS. 1 and 2.

The separator 10 shown in FIG. 1 has a separating chamber 25 havingfirst, second and third cylindrical portions 12, 14 and 16 coaxiallyarranged in that order. These cylindrical portions are generally similarto the corresponding first, second and third cylindrical portions of theseparating chamber of the cyclone separator described in theaforementioned U.S. Pat. No. 4,237,006, the disclosures of which arehereby incorporated into the present specification to form part thereof.Most particularly, the first cylindrical portion 12 has two feed pipes26, 28 associated therewith, these being arranged to feed tangentiallyinto the cylindrical portion 12 via respective inlet apertures of whichonly one aperture, namely aperture 30 associated with pipe 26, isvisible in the drawing. The two feed inlet apertures are diametricallyarranged one relative to the other and positioned close to the end ofportion 12 remote from portion 14. The end of portion 12 remote fromportion 14 also has a circular outlet opening 32 which leads to anoverflow outlet pipe 34.

Cylindrical portion 12 is connected to portion 14 by a part 12a of theseparating chamber 25 exhibiting a taper towards the second cylindricalportion 14. As explained in U.S. Pat. No. 4,237,006 however, suchtapered part is not essential.

The second cylindrical portion 14 exhibits a taper over its length,tapering from a diameter at the end adjacent portion 12 equal to thediameter of portion 12 at the junction between the two portions to asomewhat lesser dimension at its opposite end. Cylindrical portion 16 isof constant diameter equal to the minimum diameter of portion 14.

In the drawing, the length 1 of portion 12, its diameter d₁, the taperangle α of the part 12a, the internal diameter d₀ of the outlet pipe 34,the length and diameter 1₂, d₂ of the second portion 14, the taper angleβ of the second portion 14 and the length 1₃ and diameter d₃ of thethird cylindrical portion, as well as the total area A_(i) of the twofeed inlet apertures 30 may all be selected in accordance with theparameters mentioned in U.S. Pat. No. 4,237,006. These constraints are:

    10≦1.sub.2 /d.sub.2 ≦25

    0.04≦4A.sub.i /πd.sub.1.sup.2 ≦0.10

    0.1≦d.sub.0 /d.sub.2 ≦0.25

    d.sub.1 >d.sub.2

    d.sub.2 >d.sub.3

It has not been found always essential to adhere to these constraintshowever. For example the outlet diameter d₀ need not be constrained tobe within limits as described therein.

A fourth portion is added to the separating chamber 25, this portionbeing designated by reference numeral 18 in the figure. Portion 18 has apart 18a adjacent portion 16 which is of frustoconical configuration,tapering from a maximum diameter equal to d₃ at its end closest to andadjoining to the outlet end of cylindrical portion 16, to a diameter d₄at its outlet end. At the outlet end of part 18a, fourth portion 18includes an outlet pipe 18b which is of internal diameter d₄.

Preferably, the angle γ, being the conicity or half-angle of thefrustoconical surface of part 18a is about 45°, although angles in therange 30° to 60° are generally satisfactory. Various alternative formsfor the portion 18 including part 18a and pipe 18b are described in thespecification of my International Patent Application PCT/AU83/00028, thedisclosures of which are hereby incorporated to form part of the presentspecification.

In use, liquid to be separated is admitted tangentially to the interiorof cylindrical portion 12 via feed pipes 26, 28, the denser component ofthe liquid then travelling lengthwise through the separator to emergefrom pipe 18b, whilst the lighter component emerges from pipe 34. Thepipe 18b thus defines, at the end remote from part 18a, an underflow ordenser liquid outlet 23. A pump 220 such as a conventional piston pumpoperates to effect admission of the liquid to be separated, via a line106.

The overflow outlet pipe 34 is shown in more detail in FIG. 2 as havinga stepped interior bore leading from outlet opening 32. Moreparticularly, the bore has a first portion 75 adjacent outlet 32 and ofdiameter equal to the diameter of outlet 32, and a second portiondefining an orifice 77 at the end of bore portion 75 remote from outlet32, orifice 77 being of lesser diameter than bore portion 75. Orifice 77leads, at the side thereof remote from bore portion 75, to an enlargedchamber 79. Chamber 79 defines a frustoconical seating surface 81 aroundthe orifice 77. At the end of chamber 79 remote from orifice 77, thepipe 34 is provided with a threaded bore 76 and a needle valve member 80is threadedly received therein so as to extend from the exterior of thepipe 34 into the chamber 79. Chamber 79 is substantially closed at theend remote from orifice 77, by virtue of the positioning of the member80 within bore 76. However chamber 79 is open sidewardly, via an outlet84, leading to an outlet line 86. The valve member 80 is movable, byrotating the valve member in the threaded bore 76, between a position atwhich a frustoconical end surface 80a thereof engages seating surface 81to close off orifice 77 and a position at which the member 80 iswithdrawn to correspondingly move end surface 80a away from the orifice77 to allow free communication of liquid from bore portion 75 intochamber 79 via the orifice 77, for exit from the chamber 79 via outlet84 and line 86.

By the above described means, the cross sectional area presented forliquid outflow from the overflow outlet may be varied by turning thevalve element 80 to vary the position of the surface 80a thereofrelative to the valve seating surface 81. It has been found desirable toeffect such variation in order to enable proper control of the operationof the cyclone separator when in use. For example when the separator isused for separating oil and water, the quantity of oil remaining in thewater emerging from the denser liquid outlet 23 may be varied by varyingthe position of valve member 80. In practice, it has been found that itis desirable to control the position of the member 80 in a fashion suchthat, when a greater quantity of oil than is desirable is present inwater emerging from outlet 23, the member 80 is turned to withdraw itaway from valve seat 81, that is to say to increase the cross sectionalarea for liquid flow from the outlet 32 and outlet pipe 34 when oilcontent in the emergent water is found to have increased.

FIG. 3 shows the separator 10 interconnected into a control system forautomatic regulation of the position of the member 80. Moreparticularly, the member 80 is in this case connected to a gear 87 whichmeshes with another gear 88 on the output shaft of an electric motor100. Motor 100 is operated under control of a control circuit 108 froman electric current supply 110. The denser liquid or water outlet 23 ofthe separator is connected to a discharge pipe 19 provided with twoopposed windows 112, 114 whereby to permit light from a laser beamsource 116 to be passed transversely across the pipe from one window 112to exit via the other window 114. A detector 118 is arranged to receivesuch transmitted light and to generate an electric signal proportionalto the magnitude of the light intensity so detected. Detector 118 isconnected to circuit 108 so that the output signal from the detector isin use compared with a fixed signal provided from a reference generator120. The amount of light received by the detector 118 is dependent uponthe quantity of oil in water passing out through pipe 19, decreasingwith increase in oil content. The control circuit 108 operates to applyno electric supply to motor 100 from supply 110 in the event that themagnitude of the signal from detector 118 is determined, by comparisonwith the signal from the reference generator 120, to be representativeof presence of a desired level of oil contamination in the oil flowingthrough pipe 19. In the event that the magnitude of the signal fromdetector 118 should fall, indicating a rise in oil content, controlcircuit 108 operates to apply power to motor 100 whereby to turn thegears 88 and 87 in a direction causing withdrawal of member 80 away fromorifice 77 by a predetermined amount. Similarly, in the event that thesignal generated by detector 118 should rise, indicating a lesserquantity of oil than the aforementioned predetermined level, the controlcircuit 108 operates motor 100 whereby to drive the member 80 in thedirection towards the orifice 77.

In the modified arrangement of FIG. 8, the signal from detector 118 isamplified by an amplifier 190 and used to energise a solenoid 192 whichhas a toothed rack 194 attached to its plunger 196. Rack 194 meshes withgear 87 so as to drive the gear when the plunger 196 and rack are movedaxially. The plunger is biased by a spring 198 to an extended restposition established by engagement of the rack with a fixed stop member200. In use, the rack 194 and plunger 196 assume a rest postionconditional on the degree of energisation of solenoid 192. That is tosay, the current flow through the solenoid coil is increased on rise insuch current due to increase in signal from detector 118 occurring whenthe opacity of liquid passing through pipe 19 drops so that a greaterforce is exerted on the plunger 196 to draw the plunger into thesolenoid until a new rest state is reached at which the increased forceis balanced by corresponding increased resilient bias provided by thespring 198. Similarly a decrease in signal from detector 118, caused byincreased opacity of the liquid in pipe 19 weakens the force applied tothe plunger 196 to effect movement of the plunger outwardly of solenoid192 to establish a new equilibrium position. These movements of theplunger are translated to cause corresponding rotation and thuslengthwise movement of the member 80 to cause the member to move towardsorifice 77 when the detected oil content decreases and to move away fromthe orifice 77 when the detected oil content increases.

Reverting again to FIG. 3, two valves 102, 104 are shown arrangedrespectively in a line 106 supplying liquid to be separated to the inletpipes 26, 28 and in the pipe 19. Valves 102, 104 are interconnected by arecycling line 128. Valves 102, 104 are operated under control of acontrol circuit 140 which is connected to a comparator 142 receiving,the output from detector 118 and also receiving a fixed reference signalfrom a reference generator 144.

As shown in FIGS. 4 and 6, valve 102 comprises a hollow cylindrical body102a within which is arranged a rotatable cylindrical member 102b.Member 102b has internal passageways therein providing communication toand between three peripherally spaced ports 160, 162 and 166 thereof.Body 102a has three peripherally spaced ports 168, 170, 172communicating, respectively, with line 106, line 128 and an input line103 (for inlet of liquid to be separated via the valve to line 106). Asshown in FIGS. 5 and 7, valve 104 comprises a hollow cylindrical body104a having a rotatable cylindrical member 104b therein. Member 104b hasinternal passageways therein providing communication to and betweenthree peripherally spaced ports 180, 182 and 184 thereof. Body 104a hasthree peripherally arranged ports 190, 192, 194 communicating,respectively, with pipe 19, line 128 and a line 181 leading to an outletfrom the apparatus.

Under the condition where the output from detector 118 is greater than apredetermined level, indicative of less than a predetermined proportionof oil in water emerging from pipe 19, control circuit 140 operates tocondition the valves 102, 104 as shown in FIGS. 4 and 5. Moreparticularly, member 104b is positioned so that port 180 is aligned withport 190 and port 184 is aligned with port 194, whilst port 192 isclosed by the member 104b and port 182 is closed by engagement with theinterior wall of the body 104a. Also, valve 102 has its valve member102b positioned so that port 160 communicates with port 168 and port 166communicates with port 172 whilst port 170 is closed by the peripheralside wall of member 102b and port 162 is closed by the interior surfacebody 102a. Thus, flow of separated water from separator 10 can occurfrom pipe 19 through ports 190, 180, 184, 194 to line 181. Similarly,oily water to be separated can enter the separator through line 103,passing through ports 172, 166, 160, 168 of valve 102 to line 106,whilst flow to or from line 128 is blocked. In this condition, theseparator operates normally.

In the event that the signal from detector 118 should drop below apredetermined value as set by reference generator 144 (indicative of aproportion of oil in the water emerging from pipe 19 greater than theaforementioned predetermined value), comparator 142 operates tocondition circuit 140 for movement of the valves 102, 104 to conditionthem as shown in FIGS. 6 and 7. In this condition, ports 180, 182respectively provide communication to ports 192, 190 in valve 104 sothat line 128 and pipe 19 are in communication. Port 184 and port 194 ofvalve 104 are then blocked. On the other hand, valve 102 is thenconditioned so that ports 160, 162 respectively communicate with ports170 and 168, and so that lines 128 and 106 are connected together. Port166 of valve 102 is then blocked as is port 172. Thus line 103 is alsoblocked. In this case, then, water emerging from outlet pipe 23 travelsdown pipe 19 through valve 104 along line 128 to be readmitted to theseparator via line 106, pump 220 and feed pipes 26, 28. Thus, in theevent that the oil content in the emergent water from the separatorexceeds the predetermined level established by the signal from referencegenerator 144, the water emerging from the water outlet 23 of separator10, instead of being discharged via line 181 is recirculated for furtherseparation. When comparator 142 indicates that the water emerging fromoutlet 23 has a sufficiently low oil contamination level, the controlcircuit 140 reverts the valves to the position shown in FIG. 4 fornormal operation.

The described construction has been advanced merely by way ofexplanation and many modifications may be made thereto without departingfrom the spirit and scope of the invention as defined in the appendedclaims.

I claim:
 1. A cyclone separator for separating liquid components in aliquid mixture and having an elongate tapered separating chamber with atleast one side inlet for liquid to be separated and an overflow outletopening at a larger cross-sectional end of the separating chamber, foroutflow of the less dense of said components, the separating chambr alsohaving an underflow outlet at the smaller cross-sectional end of theseparating chamber, for outflow of the denser of said components, andvalve means operable to effect variable restriction of flow from theseparator via said overflow outlet opening, said separator having acontrol system coupled to said valve means to effect said variablerestriction of flow, the control system including a contaminant sensorpositioned exteriorly of said separating chamber to receive and monitorthe level of contamination of the denser of said separated components,emerging from said underflow outlet, by presence of the less densecomponent therein, said system varying said restriction to flow from theoverflow outlet in accordance with variations in said measured level ofcontamination, whereby to tend to minimize said level of contamination.2. A cyclone separator as claimed in claim 1 wherein said overflowoutlet opening is defined by an overflow outlet pipe which presents anorifice through which liquid flow from the overflow outlet openingoccurs in use of the separator, and the valve means comprises a membermovable to effect variable restriction of the orifice.
 3. A cycloneseparator as claimed in claim 2 wherein said member is movable towardsand away from the orifice to effect said variable restriction.
 4. Acyclone separator as claimed in claim 3 wherein said orifice is providedin a chamber within said overflow pipe, said member extending into saidchamber towards said orifice.
 5. A cyclone separator as claimed in claim4 wherein said chamber has a side exit opening for liquid which passesfrom said separating chamber through said orifice.
 6. A cycloneseparator as claimed in claim 5 wherein said overflow outlet openingcommunicates with said separating chamber and with a first bore portionof said overflow pipe, said orifice being defined in an end of saidfirst bore portion remote from the overflow outlet opening.
 7. A cycloneseparator as claimed in claim 6 wherein said chamber is formed as asecond bore portion in said overflow outlet pipe concentric with saidfirst bore portion and is of lesser diameter than said first boreportion.
 8. A cyclone separator as claimed in claim 7 wherein saidorifice is circular in cross section and is arranged coaxially with theaxis of said chamber and said first bore portion and said member isdefined as a needle member coaxially movable lengthwise of said chamber,orifice and first bore portion.
 9. A cyclone separator as claimed inclaim 8 wherein said needle member is threaded and is threadedlyreceived in a threaded bore extending through an end of the overflowoutlet pipe, whereby to be rotatable to effect movement of the needlemember towards and away from the orifice.
 10. A cyclone separator asclaimed in claim 9 wherein said orifice has at the end thereof withinsaid chamber a surrounding concave frustoconical valve seat and theneedle member has at its end an end surface of complementaryconfiguration whereby to seal said orifice when said needle member ismoved to bring said end surface and valve seat together.
 11. A cycloneseparator as claimed in claim 1 wherein said system acts to increaseflow from said overflow outlet opening on detection of an increase insaid contamination of said denser components by said less densecomponent and to decrease said flow on detection of a decrease incontamination.
 12. A cyclone separator as claimed in claim 11 whereinby-pass means is provided, sensitive to contamination of said densercomponent as separated by said separator, by said less dense component,to effect recycling of such contaminated denser component through theseparator.
 13. A cyclone separator as claimed in claim 12 wherein saidby-pass means comprises valve means operating, on said contaminationbeing sensed to be above a predetermined level, to divert flow from saidunderflow outlet back into said inlet.
 14. A method of controlling acyclone separator separating liquid components in a liquid mixture andhaving an elongate tapered separating chamber with at least one sideinlet for liquid to be separated and an overflow outlet opening at alarger cross-sectional end of the separating chamber, for outflow of theless dense of said components, the separating chamber also having anunderflow outlet at the smaller cross-sectional end of the separatingchamber, for outflow of the denser of said components, and valve meansoperable to effect variable restriction of flow from the separator viasaid overflow outlet opening, the method comprising measuring, by theuse of a contaminant sensor positioned exteriorly of said separatingchamber, the level of contamination of the denser of said separatedcomponents, emerging from said underflow outlet, by presence of the lessdense component therein, and operating said valve means to effect saidvariable restriction of flow the overflow outlet in accordance withvariation in said measured level of contamination, whereby to tend tominimize the level of contamination.
 15. A method as claimed in claim 14wherein said liquid mixture comprises a mixture of oil and water whereinsaid measuring comprises measuring the amount of oil in water emergingfrom said underflow outlet opening.
 16. A method as claimed in claim 15wherein said valve means is operated to increase flow from said overflowoutlet opening, on detection of an increase in said contamination, andto decrease said flow on detection of a decrease in said contamination.17. A method as claimed in claim 15 including recycling said denserseparated component through the cyclone separator on detection of agreater than desired level of contamination of that component bypresence of the less dense component therein.
 18. A method as claimed inclaim 16 including recycling said denser separated component through thecyclone separator on detection of a greater than desired level ofcontamination of that component by presence of the less dense componenttherein.